1. Field of the Invention
The present invention involves boron containing metal overbased calixarates that are useful as additives for various applications to include as multifunctional additives in functional fluids and lubricants such as engine oils for internal combustion engines.
2. Description of the Related Art
Functional fluids and lubricants generally contain one or more additives that provide required performance. Engine oil lubricants for internal combustion engines contain additives to provide detergent and antiwear performance. Basic metal salts of arylsulfonates and sulphur-coupled phenates are commonly added to engine oils to provide detergent performance. Optimum antiwear performance in engines is obtained by including a zinc dialkyl dithiophosphate in an engine oil formulation. Contrary to detergent and antiwear performance requirements, current and future engine oils are being required to gradually reduce sulphur and phosphorus content to improve exhaust emissions performance and comply with environmental regulations.
U.S. Pat. No. 5,340,369 discloses diesel fuels that contain organometallic complexes including complexes derived from a calixarene and a metal reactant where the metal can be a mixture of two or more metals that includes boron.
U.S. Pat. Nos. 5,114,601, 5,205,946 and 6174844 disclose overbased metal calixarates useful as additives to lubricating oils.
U.S. Patent No. 4,744,920 discloses borated overbased materials that are useful in lubricating oils.
U.S. Patent No. 5,635,459 discloses a functional fluid having improved gear performance that includes as one of its components an alkali or alkaline earth metal salt complex in the form of borated and/or nonborated salts.
Reviews on calixarenes are found in Monographs in Supramolecular Chemistry, by C. David Gutsche, series Editorxe2x80x94J. Fraser Stoddart, published by the Royal Society of Chemistry, 1989 and 1998.
It has now been found that the boron-containing metal overbased calixarates of the present invention are multifunctional additives that provide both detergent and antiwear performance to a functional fluid or lubricant such as an engine oil without increasing the sulphur and phosphorus content since these calixarates are free of sulphur and phosphorus.
An object of the present invention is to provide detergent and antiwear performance to a lubricant composition.
Another object of the present invention is to provide detergent and antiwear performance to a lubricant composition wherein the lubricant composition is an engine oil for an internal combustion engine.
A further object of the present invention is to provide detergent and antiwear performance to a lubricant composition without increasing the sulphur content and phosphorus content of the lubricant composition.
The objects, advantages and embodiments of the present invention are in part described in this application and in part are obvious from the application or from the practice of this invention. Therefore, it is understood that the invention is claimed as described or obvious as falls within the scope of the appended claims.
To achieve the foregoing objects in accordance with the invention as described and claimed herein, a composition comprises a boron-containing overbased metal salt of a calixarene wherein the calixarene has at least one substituent hydroxyl group capable of reacting with a metal base to form the metal salt; and the boron-containing overbased metal salt of the calixarene is free of sulphur and phosphorus.
In a second embodiment of this invention, a lubricant additive composition comprises the above described composition comprising the boron-containing overbased metal salt of the calixarene wherein the boron-containing overbased calixarate functions as a detergent and an antiwear agent.
In a third embodiment of the present invention, a lubricant composition comprises a lubricating oil and the above described lubricant additive composition.
In a fourth embodiment of this invention, a method to lubricate an internal combustion engine comprises lubricating the engine with the above described lubricant composition that includes the boron-containing overbased calixarate wherein the calixarate provides detergent and antiwear performance without increasing sulphur and phosphorus content.
In a fifth embodiment of this invention, a process to prepare the boron-containing overbased calixarate comprises reacting a calixarene or low based metal salt thereof, a metal base, a solvent as described herein, carbon dioxide, and orthoboric acid or a reactive equivalent thereof that is added before the addition of carbon dioxide.
A composition of the present invention comprises a boron-containing overbased metal salt of a calixarene wherein the calixarene has at least one substituent hydroxyl group capable of reacting with a metal base to form the metal salt; and the boron-containing overbased metal salt of the calixarene is free of sulphur and phosphorus.
A metal salt of a calixarene can be termed a metal calixarate, and the boron-containing overbased metal salt of a calixarene can be referred to as a boron-containing overbased calixarate.
The calixarene portion of the boron-containing overbased calixarate is a cyclic oligomer prepared by condensation of a hydroxyl-substituted aromatic hydrocarbon compound with a coupling reagent to form a cyclocondensation product that has a cone or calix-like shape. The hydroxyl-substituted aromatic hydrocarbon compound can have one or more hydroxyl groups to include phenols and resorcinols. The hydroxyl-substituted aromatic hydrocarbon compound can have from zero to three hydrocarbyl substituents. In one embodiment the hydroxy aromatic hydrocarbon compound has no hydrocarbyl substituents and in a second embodiment has one hydrocarbyl substituent. The hydrocarbyl substituent is a univalent radical that contains one or more carbon atoms and is predominately hydrocarbon in nature, but can have heteroatoms in the hydrocarbon chain and can have nonhydrocarbon groups such as a hydroxyl group attached to the hydrocarbon chain. The hydrocarbyl substituent can have on the average 1 to 215 carbon atoms and in other embodiments on average 2 to 100 carbon atoms, 4 to 50 carbon atoms, and 8 to 30 carbon atoms. The hydrocarbyl substituent can be derived from an olefin such as isobutylene, or a mixture of two or more olefins. The hydrocarbyl substituent can be derived from a polyolefin such as a polypropylene tetramer or a C18 polyethylene, or a mixture of two or more polyolefins. The polyolefin can be a homopolymer from a single olefin monomer, a copolymer from a mixture of two or more olefin monomers, and includes mixtures of homopolymers and copolymers. The hydrocarbyl substituent can also be derived from a mixture of an olefin and a polyolefin such as a mixture of isobutylene and a polypropylene tetramer. Alternatively to using mixtures of olefins and/or polyolefins, a first hydroxyl aromatic compound can be alkylated with a first olefin or polyolefin, a second hydroxyl aromatic compound can be alkylated with a second olefin or polyolefin, and then the two alkylated hydroxyl aromatic compounds can be admixed. The hydrocarbyl substituent can be a straight chain, a branched chain, or mixtures thereof. Hydrocarbyl-substituted hydroxy-substituted aromatic hydrocarbon compounds can be prepared by well known procedures such as a Lewis acid catalyzed alkylation reaction of phenol with an olefin or polyolefin.
The coupling reagent used to prepare the calixarene can be an aldehyde such as formaldehyde or acetaldehyde, a ketone, a sulfurizing agent such as elemental sulphur, a dihaloalkane, a dihydroxyalkane, or mixtures thereof.
The number of repeating units of the hydroxy-substituted aromatic hydrocarbon compound in the calixarene can be at least 3 and in other embodiments of the invention can be at least 4, or 3 to 12, or 4 to 12. In another embodiment of the present invention the calixarene can be a mixture of cylic oligomers having different numbers of repeating units of the hydroxy-substituted aromatic hydrocarbon compound such as a mixture of 4 and 6 repeating units or a mixture of 6 and 8 repeating units termed respectively a calix[4,6]arene and a calix[6,8]arene.
In an embodiment of the present invention the calixarene portion of the boron-containing overbased metal salt of the calixarene can be represented by the formula 
where Y is a divalent group; either R1 is hydroxyl and R2 and R4 are independently hydrogen or hydrocarbyl or R1 is hydrogen or hydrocarbyl and R2 and R4 are hydroxyl; R3 is hydrogen or hydrocarbyl; and n is 3 to 12. The divalent group Y is derived from the coupling agent used to form the calixarene and can be hydrocarbylene, a sulphide or polysulphide, or mixtures thereof. The hydrocarbylene group is defined the same as hereinabove for the hydrocarbyl substituent except that the hydrocarbylene group is a divalent radical of one or more carbon atoms, usually 1 to 10 carbon atoms. In another instance Y is a methylene, R1 is hydroxyl, R2 and R4 are hydrogen, and R3 is an alkyl group having an average of 4 to 50 carbon atoms.
In a further embodiment of this invention the calixarene is prepared from a hydrocarbyl-substituted phenol and an aldehyde. In a further instance of the invention the hydrocarbyl-substituted phenol is on average a C10-C24 alkylphenol, the aldehyde is formaldehyde or a reactive equivalent thereof, and the number of repeating phenolic units in the calixarene is 4 to 12.
Calixarenes of the present invention can be prepared by reacting a hydroxy-substituted aromatic hydrocarbon compound such as an alkylphenol with a coupling reagent such as an aldehyde in the presence of a base by the method described in Monographs in Supramolecular Chemistry by C. David Gutsche, Series Editorxe2x80x94J. Fraser Stoddart, published by Royal Society of Chemistry, 1989 and 1998.
The metal of the metal salt or of the overbased metal salt of the calixarene can be any metal or reactive equivalent thereof that is capable of forming a salt with the calixarene. Thus, metals of the present invention include both elemental metals as well as metal compounds that can form a salt with the calixarene. In an embodiment of the present invention the metal is a univalent metal, a divalent metal, or a mixture thereof. In another embodiment of the invention the metal is an alkali metal, an alkaline earth metal such as calcium, or a mixture thereof such as calcium with lithium, sodium, or potassium.
The overbased metal salt of the calixarene will contain an excess of equivalents of basic metal relative to acid equivalents from the calixarene and any co-substrates as described herein below such as a carboxylic acid. Typically the overbased calixarate will contain greater than 1.2 equivalents of basic metal per equivalent of acid, and can contain 4.5 or greater equivalents of basic metal per equivalent of acid.
The boron-containing overbased metal salt of the calixarene can be prepared by reacting the overbased calixarate with orthoboric acid or a reactive equivalent thereof. In another embodiment of the invention the boron-containing overbased calixarate is prepared by adding orthoboric acid or a reactive equivalent thereof to the calixarene and then overbasing this admixture. The boron content of the boron-containing overbased metal salt of the calixarene can be 0.05 to 5% by weight, and in other embodiments of the invention can be 0.06 to 2.5% by weight and also 0.07 to 2% by weight.
A lubricant additive composition of the present invention comprises the boron-containing overbased metal salt of the calixarene that functions as a detergent and an antiwear agent. The boron-containing overbased calixarate functions as a detergent in part due to its basicity reserve and in part due to its bipolar hydrophilic, lipophilic composition. The boron-containing overbased calixarate also functions as an antiwear agent, as demonstrated in the examples hereinbelow, partly due to the overbased calixarate and partly due to the further presence of a borate component in the overbased calixarate. The lubricant additive composition can further comprise a lubricating oil as described hereinbelow. The lubricating oil can serve as an inert reaction solvent during preparation of the boron-containing overbased calixarate and later as a dilutent to facilitate handling and transfer of the lubricant additive composition. The lubricating oil in the lubricant additive composition can range from 0 to 90% by weight, but more commonly ranges from 5 to 60% by weight.
A lubricant composition of the present invention comprises a lubricating oil and the lubricant additive composition that comprises the composition comprising the boron-containing overbased metal salt of the calixarene as described throughout this application. The lubricant composition can be used in any application that benefits from a lubricant additive composition that functions as a detergent and an antiwear agent. Applications where the lubricant composition can be used include engine oils for all types of internal combustion engines, gear oils, metalworking fluids, transmission fluids, hydraulic fluids, and greases. The lubricant composition can be used in any application that benefits from a lubricant additive composition that functions as a detergent and antiwear agent without increasing the sulphur content and/or the phosphorus content of the lubricant composition. The lubricant composition of the present invention is especially useful in engine oils for internal combustion engines where there is a requirement to reduce the sulphur and phosphorus content to improve engine exhaust emissions to meet environmental standards.
The amount of the boron-containing overbased metal salt of the calixarene in the lubricant composition will be an amount that provides detergent and antiwear performance. The content of the boron-containing overbased calixarate in the lubricant composition can be 0.1 to 50% by weight, and in other embodiments can be 0.2 to 20% by weight, 0.3 and 10% by weight, and 0.5 to 7% by weight.
The lubricating oil of the lubricant composition can be any oil or combination of oils, to include natural and synthetic oils, that functions as a lubricating oil in the lubricant composition. The lubricating oil can be various types of unrefined and refined mineral oils to include oils in the American Petroleum Institute Base Oil Groups I, II, III and V, polyolefins to include poly(alpha-olefins) and olefin copolymers, esters of carboxylic acids such as diisodecyl azelate, alkylated aromatic hydrocarbons such as dodecylbenzene, animal oils, vegetable oils, polymers of alkylene oxides and ester and ether derivatives thereof, silicon-based oils to include various silicones, and esters of phosphorus based acids such as phosphoric and phosphonic acids. The lubricating oil is generally present in the lubricant composition in a major amount of 50% or more by weight, and in other embodiments of the invention can be present at 75% or more by weight, or at 95% or more by weight.
The lubricant composition can also contain one or more additional lubricant additives depending on the application that the lubricant composition is intended to be used for. The lubricant composition can further comprise at least one lubricant additive composition selected from the group consisting of a detergent, a dispersant, an antiwear agent, an antioxidant, a corrosion inhibitor, a friction modifier, a foam control agent, and a viscosity modifier to include viscosity index improvers and pour point depressants.
In another embodiment of this invention the lubricant composition is an engine oil for an internal combustion engine. In further embodiments of the invention the engine oil has a sulphur content below 0.5% by weight, below 0.3% by weight, or below 0.2% by weight. In still further embodiments of this invention the engine oil has a phosphorus content below 0.1% by weight, below 0.07% by weight, or below 0.05% by weight.
A method of the present invention to lubricate a device or system comprises lubricating the device or system with the lubricant composition that contains the boron-containing overbased calixarate which provides detergent and antiwear performance without increasing the sulphur content and the phosphorus content of the lubricant composition. In another embodiment of the invention a method to lubricate an internal combustion engine comprises lubricating the engine with the lubricant composition that contains the boron-containing overbased metal salt of the calixarene that provides detergent and antiwear performance without increasing the sulphur content and phosphorus content of the lubricant composition.
A process of the present invention to prepare the boron-containing overbased metal salt of the calixarene comprises reacting at an elevated temperature the calixarene or a low based metal salt thereof; a metal base that is added in one or more than one addition during the reaction; a solvent comprising (a) a polyhydric alcohol or a poly-(alkylene glycol) optionally in combination with a hydrocarbon solvent, a mineral oil, water, a monohydric alcohol, a carboxylic acid ester, a ketone, or an ether, or (b) a monohydric alcohol in combination with a hydrocarbon solvent or a mineral oil; carbon dioxide that is added in one or more than one addition after the addition of the metal base; and orthoboric acid or a reactive equivalent thereof that is added before the addition of carbon dioxide.
The process of preparing the boron-containing overbased calixarate can use as a reactant the calixarene, a low based metal salt of the calixarene, or a lesser overbased metal salt of the calixarene. A low based metal salt of the calixarene will generally contain from less than 1 to 1.2 equivalents of basic metal per equivalent of acid from the calixarene and any acidic co-substrates. In other embodiments of the present invention the equivalents of basic metal per equivalent of acid in the low based calixarate can range from 0.1 to 1.2, from 0.5 to 1.2, and from 0.8 to 1.2.
The metal base used to prepare the boron-containing overbased calixarate can be any metal base or reactive equivalent thereof that can form a metal salt with the calixarene to include elemental metals and metal compounds. Especially useful as metal bases are alkali and alkaline earth metal compounds to include alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides such as sodium hydroxide, magnesium oxide and calcium hydroxide.
The solvent used in the reaction to prepare the boron-containing overbased calixarate can comprise a polyhydric alcohol or poly(alkylene glycol) such as ethylene glycol, diethylene glycol, or the methyl ether of diethylene glycol optionally in combination with a hydrocarbon solvent such as toluene or xylene, a mineral oil, water, a C1-C20 monohydric alcohol, a carboxylic acid ester such as ethyl acetate, or an ether. Alternatively the solvent can comprise a C1-C4 monohydric alcohol such as methanol in combination with a hydrocarbon solvent or a mineral oil. U.S. Pat. No. 5205946 describes in detail a solvent that can be used to prepare the boron-containing overbased calixarate. The solvent is generally added to the reaction mixture prior to starting the reaction, but can also be added throughout the reaction to facilitate processing.
Orthoboric acid H3BO3 or a reactive equivalent thereof can be used to prepare the boron-containing overbased metal salt of the calixarene. Reactive equivalents of orthoboric acid include organo borate esters such as the trialkyl borate ester tri(2-ethylhexyl) borate, boric acid anhydrides such as a metaboric acid HBO2 and boron oxide B2O3, and metal borate salts such as borax Na2B4O7.10H2O.
The process of preparing boron-containing overbased calixarates, in which orthoboric acid or a reactive equivalent thereof is added before the addition of carbon dioxide and before the start of the preparatory reaction, is detailed in the examples herein-below. In another embodiment of the invention, boron-containing overbased calixarates are prepared by adding orthoboric acid or a reactive equivalent thereof after the addition of carbon dioxide and after the calixarene is overbased. U.S. Pat. Nos. 5205946 and 4744920 respectively detail a procedure for preparing an overbased metal salt of a calixarene and a procedure for preparing a boron-containing overbased material by reacting an overbased material with a borating agent such as orthoboric acid.
The boron-containing overbased metal salt of the calixarene of the present invention can contain at least one co-substrate selected from the group consisting of a C6-C100 carboxylic acid or anhydride thereof such as tall oil fatty acids, a C12-C100 polycarboxylic acid or anhydride thereof such as octadecenylsuccinic anhydride, a hydrocarbyl-substituted phenol such as a dodecylphenol, a hydrocarbyl-substituted sulphonic acid, a hydrocarbyl-substituted salicylic acid, and a hydrocarbyl-substituted naphthenic acid. The co-substrates can be added any time during the preparation of the boron-containing overbased calixarate, but are normally added before the start of the preparatory reaction.
The lubricant additive composition and lubricant composition of the present invention are generally prepared by blending or mixing the components at ambient temperature to elevated temperatures of 40 to 100xc2x0 C. until the resultant composition is homogeneous.